An historical side note: the first time I heard the phrase "hate speech" was in the early 70s. It was used in a discussion of some issue or other by a member of the Socialist Worker's Party, a Trotskyist aligning Marxist group.
At the time I laughed seeing how a Marxist, of all people, was calling for the suppression of "hate speech" (what else to they engage in?), and the implications for free speech. I am not laughing now.
Those of us now 50 years old and older are likely the last ones taught primarily by non PC teachers in K-12 grade. While our fathers fought WW2 these tyrants were taking us over from within our own nation. They got established in colleges and universities as professors by the late 1950’s and eventually carried over into the military and elected offices as well. PC is merely a tool they used and it's been quite effective. It brought us campus riots of the 60’s and 70’s. The Great Society & decline to follow was the icing on the cake to give it an iron clad foot hold.
PC was becoming prevailent in the military even in the 1970's. If your evaluations didn't contain supporting certain PC programs it was a black mark.